Exhaust gas turbochargers are used to boost the output of internal combustion engines. In modern internal combustion engines, matching the exhaust gas turbocharger to variable operating conditions is becoming increasingly more difficult. So-called variable turbine or compressor geometry offers one popular possibility. In a variable turbine geometry the guide vanes of the guide apparatus are aligned more or less steeply to the flow upstream of the turbine wheel according to the turbine power demand. In variable compressor geometry the diffusor vanes are aligned more or less steeply to the flow downstream from the compressor wheel. The vanes are generally adjusted via so-called adjusting levers which are moved by an adjusting ring located concentrically to the axis of the exhaust gas turbocharger. For radial turbines or radial compressors the guide vane or diffusor vane is generally parallel to the shaft axis. The shaft of the guide or diffusor vane is preferably supported twice in a housing and is turned by means of an adjusting lever which acts on the vane shaft between the two bearing points. DE 102 09 172 shows a conventional adjustable guide apparatus in which the adjusting lever after mounting the vanes is slipped onto the vane shaft and then fixed. The vane shaft can also be supported by means of an individual hole, as described in EP 1 396 621. Here the adjusting lever is also mounted subsequently after inserting the vanes.
The precisely machined joint between the slipped-on adjusting lever and the blade shaft on the one hand causes additional costs and on the other hand reduces the operating reliability of the adjustment mechanism. Relative movements which can consequently lead to wear over a longer operating time occur in the connection due to the production- and installation-induced plays.
EP 1 234 950 A1 discloses a guide device with adjustable guide vanes which are made in one piece and which are pivotally supported in hemispherical bearing openings which are opened on one aide. The bearing openings are closed with a straight cover so that the guide vanes do not fall out with the corresponding loading in the direction of the cover. In the area of the cover the bearing points of the guide vanes experience high surface pressure due to the linear support. This can lead to wear phenomena on the guide vanes and bearing opening.